22,478 research outputs found

    Simulating Electron Transport and Synchrotron Emission in Radio Galaxies: Shock Acceleration and Synchrotron Aging in Three-Dimensional Flows

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    We present the first three-dimensional MHD radio galaxy simulations that explicitly model transport of relativistic electrons, including diffusive acceleration at shocks as well as radiative and adiabatic cooling in smooth flows. We discuss three simulations of light Mach 8 jets, designed to explore the effects of shock acceleration and radiative aging on the nonthermal particle populations that give rise to synchrotron and inverse-Compton radiations. We also conduct detailed synthetic radio observations of our simulated objects. We have gained several key insights from this approach: 1. The jet head in these multidimensional simulations is extremely complex. The classical jet termination shock is often absent, but motions of the jet terminus spin a ``shock-web complex'' within the backflowing jet material of the head. 2. Understanding the spectral distribution of energetic electrons in these simulations relies partly upon understanding the shock-web complex, for it can give rise to distributions that confound interpretation in terms of the standard model for radiative aging of radio galaxies. 3. The magnetic field outside of the jet itself becomes very intermittent and filamentary in these simulations, yet adiabatic expansion causes most of the cocoon volume to be occupied by field strengths considerably diminished below the nominal jet value. Thus population aging rates vary considerably from point to point.Comment: 44 pages, 6 figures; to be published in the Astrophysical Journal (August 2001); higher-quality figures can be found at http://www.msi.umn.edu/Projects/twj/radjet/radjet.htm

    Work-Life Reconciliation Policies From Well-Being To Development: Rethinking EU Gender Mainstreaming

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    Across the European Union (EU), gender policies are cross-cutting initiatives incorporated within the major axes of regional operational programs, and specifically, within active labor-market, local development and inclusion policies. This is the so-called gender mainstreaming across EU Structural Funds, calling for increasing policy instruments integration. The aim of this paper is to understand if and how to improve women’s well-being and subsequently participation in collective action through reconciliation policies. These measures aim to allow women and men to choose how they can reconcile family care, paid work, career advancement, and leisure. The idea is that such a choice implies a time allocation pattern, which is not exclusively determined by market mechanisms and/or policy measures, but also by cultural trajectories, moral values, intrinsic motivations and rules (Folbre, Nelson 2002; North, 2005; Witt 2003), varying across regions and within groups. Furthermore, the outcomes of this choice are not completely internalized as individual well-being but they can also create positive externalities. First, this paper reconstructs reconciliation policies and their governance structures across less-developed regions in Italy (so-called EU Objective 1 areas) within the EU programming phase 2000-2006. Drawing upon this reconstruction, out analysis seeks to account for differences in both contextual conditions and individual characteristics, which, in turn, shape regional development processes. Second, the paper focuses on the design of conciliation policies to unveil what underlying microeconomic premises explain the expected beneficiaries’ behavioural change. Departing from the inadequacy of standard economics, whereby work-life reconciliation would be reduced to a unique choice pattern at the individual level, the paper examines those factors of subjective identities and contextual characteristics that actually affect work-life reconciliation choices, and by this way they can have a development impact (Bowles 1998, Ray, 2000, Sen 1999). In fact, the traditional public choice approach to gender policy may not only perpetuate a male-dominated structure of socioeconomic relations but it may also keep the economy working at a less efficient level. In other words, reconciliation policies may end up reinforcing a path dependent equilibrium of low efficiency, accentuating institutional, economic, social, and cultural traps (Bowles, Durlauf and Hoff 2006). By contrast, our idea is that reconciliation policies can work as development policies as long as they alter current power structures and enhance women capabilities. Building upon this critical review of the existing gender policy framework, we put forward a cognitive framework for work-life reconciliation as a driving force to development.Microeconomic behaviour; Gender Mainstreaming; Intrinsic Motivations; Local Development; Conciliation; Power Structures

    Labour market in the Catalan cotton textile sector: Employment and fertility (1850-1913)

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    This paper deals whit the dynamics of the Catalan textile labour market (the Spanish region that concentrated most of the industrial and factory activity during the 19 Century) and offers hypotheses and results on the impact it had on living standards and fertility levels. We observe the formation of an uneven labour market in which male supply for labour (excluding women and children) grew much faster than the demand. We stress the fact that labour supply is very dependant on institutional factors liked to the transmition of household property between generations. Instead the slow path of growth of adult males demand for labour is witnessing the limits of this industry to expand and to compete in international markets. The strategy of working class families to adapt to scarce opportunities of employment we document here is the diminution of legitimate fertility levels. Fertility control is the direct instrument we think workers have to control their number in a situation that was likely to create labour surpluses in the short and mid run.Labour market, female employment, children employment, fertility

    The Collective Object: Realizing Collective Space in an Era of Bigness

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    Architecture reacted to the Technological Revolution of the late 19th century with inspired proposals of optimistic expectation for the new era. The advancements of elevators, escalators and air conditioning meant almost limitless potential for the scale and scope of the built environment. However, society quickly realized the advantageous reality of this technology: Their buildings no longer needed the cities which surrounded them. Endless interiors and “cities-within-cities” meant the possibility of a lifestyle where people could choose to never again interact with the undesirables of the true city. The built environment actively resisted the collective. A trend of self-interested architectures affected urban societies with a cultural shift towards the exclusion that their cities embodied. This phenomenon, termed “Bigness” by Rem Koolhaas, is also linked to his essay, “Atlanta”, where he critiqued John Portman’s network of sky bridges for producing this supremacist phenomenon and suggested Atlanta as “the real city at the end of the 20th century”. By studying the evolution and devolution of the collective objects which once gathered the masses of society, this research seeks to understand how the loss of these spaces links to shifts in cultural values throughout history. This leads to an awareness of how “Bigness” affects a disposition of exclusion in contemporary culture. This thesis proposes to revitalize the gathering potentials of the city to create a culture of inclusion through the design of a new collective object in an era of architectural “bigness”

    Economic resilience : including a case study of the global transition network

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    This paper explores the dynamic properties of organisms and ecosystems that make them so resilient and capable of adapting to changing circumstances, allowing them to maintain an overall condition of coherence, wholeness and health while living in balance within the resources of the planet. Key principles of resilient ecological systems are explored including: self-regulation; positive and negative feedback; diversity; scale and context; cooperation; emergence and novelty; and ecological tipping points. In contrast, market based economic systems can produce unstable growth with unintended destruction of cultural and species diversity and homogenisation of global life-styles. The paper re-examines fundamental economic principles using insights from biological evolution and ecosystem dynamics to establish a foundation for more resilient economies. This involves experimenting with different models in different communities to find patterns of sustainable production and exchange appropriate to local regions. Fundamental steps in this direction include the emergence of self-organising local communities based on creative experimentation, re-localisation of core sectors of the economy (food, energy, health and education), evolution of local currencies and banking practices that support local enterprise and investment in green technologies, stimulation of decentralised renewable energy networks and economic reform aligned with ecological principles. The Transition Network provides a case study of an international community based movement that has been experimenting with putting some of these principles into practice at the local level. The aim of the Transition Network is to support community led responses to peak oil and climate change, building resilience and well-being. The concept of ecological resilience and its application to local economy is hard wired into the values and emerging structure of the network of transition communities across the globe. The movement started in the UK in 2005 and there are now over 1000 Transition initiatives spanning 34 countries across the world. Many attribute the success and phenomenal growth of the Transition Network to its emerging holographic structure that mimics cell growth within living organisms. Growing a more resilient food system in the face of the twin challenges of natural resource scarcity and climate change is central to the Transition movement. A set of principles for a post carbon resilient food economy in the UK are offered. These include an 80% cut in carbon emission in the food sector by 2050, agricultural diversification, prioritization of farming methods that establish and enhance carbon sinks, phasing out of dependence on fossil fuels in food growing, processing and distribution, promoting access to nutritious and affordable food, as well as promoting greater access to land for growing food in urban and peri-urban areas. Practical examples of Transition related projects in the food sector are presented across the following themes: access to land, low carbon production methods, food distribution systems, health and community gardens and orchards, and collaborative ownership models

    A unified theory of truth and reference

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    The truthmaker theory rests on the thesis that the link between a true judgment and that in the world to which it corresponds is not a one-to-one but rather a one-to-many relation. An analogous thesis in relation to the link between a singular term and that in the world to which it refers is already widely accepted. This is the thesis to the effect that singular reference is marked by vagueness of a sort that is best understood in supervaluationist terms. In what follows we show that the supervaluationist approach to singular reference, when wedded to the truthmaker idea, yields a framework of surprising power, which offers a uniform set of solutions to a range of problems regarding identity, reference and knowledge, problems which have hitherto been dealt with on an ad hoc basis

    Re-Discovering the Pre-Settlement Landscape: Making the Oak Savanna Real

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    Land, freedom and the making of the medieval West

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    In the course of the fifth and sixth centuries, barbarian warbands acquired property rights in the former provinces of the Roman west, in a process that established the broad structural characteristics of early medieval society in western Europe: that is the central contention of this essay. Focusing on the western Mediterranean heartlands of the Imperial government and senatorial aristocracy, it argues that these property transfers were fundamental to the emergence of ethnic identity as the crucial political marker in the post-Roman west. Latent conflict over the respective rights and obligations of barbarian ‘guests’ and their provincial ‘hosts’ structured the first attempts at post-Roman state-formation in the west, for the nature of the ‘hospitality’ offered to barbarian warbands accommodated within the Empire became a matter of contention as second and third generation ‘guests’ continued to enjoy the fruits of the property of their ‘hosts’. Interpreting these new social relationships in the light of established legal forms, barbarian kings identified agreed mechanisms for the legitimate transfer of Roman property to their followers: this process allowed Roman landowners to seek remedies for illegitimate or violent seizure, but at the price of acknowledging a significant redistribution of land to a new class of barbarian soldiers whose liberty was rooted in their military service. The result was the emergence, by the seventh century, of regionalised and militarised elites who appropriated the language of ethnicity to legitimate their position

    Forever Wild : Wilderness Values and Historic Preservation in the Catskill Forest Preserve

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    Article XIV of the New York State Constitution (1894) declares that the Adirondack and Catskill Forest Preserves will be “forever kept as wild forest lands.” The State of New York has interpreted this “forever wild” clause to mean that most structures are inherently incompatible with the wilderness values of the preserves. As a result, the State has sought to enhance wilderness by removing structures it deems “non-conforming” with the forest preserves’ natural qualities. Approaching the Catskill Forest Preserve as a cultural landscape, this thesis describes and analyzes the current and past enabling (or disabling) environment of historic preservation in the preserve and offers remedies that might increase the preservation of cultural resources. Key elements of the narrative include a human history of the Catskills region, an analysis of wilderness theory as applied to American public lands, an evaluation of legislative and management practices of the preserve, case studies of recent preservation successes, and recommendations for future management of heritage resources in the Catskill Forest Preserve
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